Web template system
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A Web template system describes the software and methodologies used to produce web pages and for deployment on websites and delivery over the Internet. Such systems process web templates, using a template engine. It is a web publishing tool present in content management systems, software frameworks, HTML editors, and many other contexts.
A web template system is composed of:
- A Template engine: the primary processing element of the system;
- Content resource: any of various kinds of input data streams, such as from a relational database, XML files, LDAP directory, and other kinds of local or networked data;
- Template resource: web templates specified according to a Template language;
The template and content resources are processed and combined by the template engine to mass-produce web documents. For purposes of this article, web documents include any of various output formats for transmission over the web via HTTP, or another internet protocol.
Motivations and typical uses
Various agencies and organizations use web template systems for mass-production of content when slower production alternatives prove unfeasible.
For an introductory overview, a news website is used as example. Suppose a "static website", where all web pages are static, and built by a web designer, that need to add and update pages every day.
A typical strategy to automate the web-designer's "repetitive work" is:
- choose a web template system to maintain the website;
- group news items with different presentation needs;
- specify the "presentation standards" through web templates, for each group of news;
- specify a content resource to generate or update the content of each news item.
Separation of concerns
For the web designer, when each web page comes from a web template, he/she can think about a modular web page structured with components that can be modified independently of each other. These components may include a header, footer, global navigation bar (GNB), local navigation bar, and content well.
For other members of the "site team", a template system frees webmasters to focus on technical maintenance, content suppliers to focus on content, and for all of them more reliability.
Moreover, it has the following advantages to its use:
- Ease of design change: presentation variations on templates are "content invariant", web designer can update presentation without another preoccupations.
- Ease of interface localization: menus and other presentation standards are ease to make uniform, for users browsing on the site.
- Possibility to work separately on design and code by different people at one and the same time.
Kinds of template systems
There are many public software and commercial packages promoted as being web templates and template engines, but there are a high diversity of disperse kinds of solutions. To select and group them in a systematic way, the first step is to characterize them as template systems.
A second step is to group and identify main properties of each characterized system:
- The architecture of these systems, into a client-server reference model, is the main division criteria for group then -- although the use of diverse modern web cache strategies, architectures can be characterized. There are, as illustrated, three groups: Outside server systems, Server-side systems, and Distributed systems.
- Main attributes:
- Template languages may be:
- Embedded or Event-driven.
- Simple, Iterable, Programmable, or Complex.
- Specification possession: the standards of the language are controlled by a public or not-public. The possession strategy and the ownership indicate the stability and credibility of the specification. Note that in most jurisdictions language specification cannot be copyrighted, so the possession is not absolute.
- Template engine possession: it is public or not (ownership rights), indicating if source codes of the template engine are open, or not.
- Template languages may be:
Outside server systems
HTML editors are the typical systems using outside server subsystems. They also commonly include themes in place of CSS styles. In general the template language is to be used only with the editor's software.
|Dreamweaver||Macromedia||HTML authoring. Embedded iterable language.|
|FrontPage||Microsoft||HTML authoring. Embedded iterable language.|
Many server-side template systems have the option to publish the output pages on the server, where the published pages will be static. It is a common feature on content management systems, like Vignette. But this does not have to be considered an out-server generation.
In the majority of the cases, this "publish option" not interferes with the template system, and it can be made by external software, as Wget.
Server-side dynamic pages began generated by templates with pre-existent software adaptated for this task. This early software was the preprocessors and macro languages, adapted for the web use, running on CGI. Next, a simple but relevant technology was the direct execution made on extension modules, started with SSI.
A lot of template systems are typically used as server-side template systems:
Technically, the methodology of embedding programming languages within HTML (or XML, etc.), used in many "server-side included script languages" are also templates. All of them are embedded complex languages.
|JavaServer Pages (JSP)||Public, Java platform.|
|C preprocessor||Public. Embedded iterable language.|
|M4||Public. Embedded complex language.|
Many web browsers support applying XSLT stylesheets to XML data in the browser itself, providing template functionality in the browser.